If the exhaust gas is not smelling like rotten egg it could be the midpipe exhaust gasket. That was the problem with mine. Have your friend change out the 2 donut gaskets in the midpipe section of the exhaust. You can get the gasket from the dealer or Autozone for about $12.00 for the set.

I have a 2006 GS430 with 90000mi.
I have the same code. Exhause doesn't smell like anything bad.
I MAY have power loss but I haven't pushed the car hard.
I guess I will do a scan on the O2 sensors and see which ones values are fluctuating

I have a 2006 GS430 with 90000mi.
I have the same code. Exhause doesn't smell like anything bad.
I MAY have power loss but I haven't pushed the car hard.
I guess I will do a scan on the O2 sensors and see which ones values are fluctuating

Do u fit the problem with code P0430?? I have the same problem, but I change all gasket and when I say all was all to avoid to the 3 light pop out again on the dash. But no was that :-(. I buy both O2 sensor up and low ones, installing and 3 days later the light show op again. I don' t what else I can do about it. I not smell nothing at all (rotten egg) on the rear pip or muffler My muffler guy check for leak and nothing.. Not leak?? Help please I hate see that 3lights on my dash Also, the gas miles on my car decreased and I fill that the engine loses some power? any help please.

I've replaced all of the sensors and switched back to premium. Wifey was putting regular in there. I still get the check engine light from time to time....but I did some research and it's from leaks in the exhaust. Turns out a leaky exhaust will trip the same code "exhaust inefficiency". Your exhaust may have a leak somewhere...prolly right at the 02 bung or at the header flange. There is a gasket there. I'll keep patchn' it till I decide to keep or sell it. it's a 98 and only got 130k on it so I'd like to spin it up to 200k before I get rid of it.

On the GS300 there are 4ea 02 sensors. The ones BEFORE the cat are used by the ECM to trim fuel and such to obtain the correct air/fuel ratio. The ones after the cats are there to check the efficiency of the cats only. If you are smelling rotten eggs and all that jazz, then it is not a cat, its a fuel trim problem. The egg smell is the cat having to burn all the hydrocarbons being pushed through the engine that did not ignite during the compression/ignition cycle. Rotten egg smell does NOT mean a bad cat. But if you continue to drive it with this condition, you will eventually plug up the cat. Prem fuel is a must. The ECM will retard the living crap out of the timing when you run low/mid grade fuel due to detonation inside the combustion chamber "click" sound. The byproduct is a very late spark/burn resulting in excessive unburnt hydrocarbons entering the exhaust system.......rotten eggs incoming..

A leak in the exhaust manifold flange will cause the pre cat 02 sensor to see a false "lean" condition due to the venturi effect of the exhaust pulling in fresh air from the leak. Once the ECM sees this "lean" condition from the pre cat 02, it will then increase injector pulse length to help buffer off the ratio skew and return the air fuel ratio to its preset parameter loaded in the prom. Since essentially, the motor is not running lean in the first place...its just additional fresh cooler air being sucked into the exhaust...you will end up with a rich condition due to to ECM compensation for the false "lean", and again the cat having to overwork to burn the extra hydrocarbons pumped into the exhaust.

An exhaust leak after the 02 sensors will causing nothing more than irritating sound, hence the reason you can change all your exhaust after the cats and not effect emissions...e.g. resonator delete and the like.

OMG, im SOOO sick of hearing everyone saying their about to replace their CAT converters just because the check engine light says the word CAT on it, people freak out. I cant even count how many times I told somebody replace their O2s first if its not an exhaust leak. And to think they were going to charge you over $1,000 for a piece of **** aftermarket CAT thats not worth pennies compared to stock. they were going to make like $800 labor off you. Do some research people! Thank god for clublexus!

On the GS300 there are 4ea 02 sensors. The ones BEFORE the cat are used by the ECM to trim fuel and such to obtain the correct air/fuel ratio. The ones after the cats are there to check the efficiency of the cats only. If you are smelling rotten eggs and all that jazz, then it is not a cat, its a fuel trim problem. The egg smell is the cat having to burn all the hydrocarbons being pushed through the engine that did not ignite during the compression/ignition cycle. Rotten egg smell does NOT mean a bad cat. But if you continue to drive it with this condition, you will eventually plug up the cat. Prem fuel is a must. The ECM will retard the living crap out of the timing when you run low/mid grade fuel due to detonation inside the combustion chamber "click" sound. The byproduct is a very late spark/burn resulting in excessive unburnt hydrocarbons entering the exhaust system.......rotten eggs incoming..

A leak in the exhaust manifold flange will cause the pre cat 02 sensor to see a false "lean" condition due to the venturi effect of the exhaust pulling in fresh air from the leak. Once the ECM sees this "lean" condition from the pre cat 02, it will then increase injector pulse length to help buffer off the ratio skew and return the air fuel ratio to its preset parameter loaded in the prom. Since essentially, the motor is not running lean in the first place...its just additional fresh cooler air being sucked into the exhaust...you will end up with a rich condition due to to ECM compensation for the false "lean", and again the cat having to overwork to burn the extra hydrocarbons pumped into the exhaust.

An exhaust leak after the 02 sensors will causing nothing more than irritating sound, hence the reason you can change all your exhaust after the cats and not effect emissions...e.g. resonator delete and the like.